ML20248C068

Forwards Responses to Questions Re Shaff Concerns Described in on Mark I Containment Sys & Evacuation Plans for Plant

ML20248C068
Person / Time
Site:	Quad Cities
Issue date:	04/06/1989
From:	Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO)
To:	Tauke T HOUSE OF REP.
Shared Package
ML20248C072	List: ML20248C068 ML20248C080
References
CCS, NUDOCS 8904110115
Download: ML20248C068 (7)

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,,,,, April 6, 1989 The Honorable Tom Tauke

. United States House of Representatives Washington, D.C. 20515

Dear Congressman Tauke:

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In response to your inquiry of February 27, 1989, we are providing you ~

with some information regarding Mr. Shaff's concerns, as described by him in a l l

letter to you dated February 1,1989. His specific questions about the Mark I 1 containment system and evacuation plans for'the Quan Cities Nuclear Power Station (QCNPS), and our responses to them, are detailed in the Enclosure. We hope that you will find this information useful in your further dealings with Mr. Shaff.

Sincerely,

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,/ ',- 'r d $' f Vicfor Stello, Jr.- ~

Executive Director for Operat' m s

Enclosure:

Responses to Questions on Containment Failure I

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April .6c 1989 The Honorable Tom Tauke United States House of Representatives Washington, D.C. 20515

Dear Congressman Tauke:

In response to your inquiry of February 27, 1989, we are providing you with some information regarding Mr. Shaff's concerns, as described by him in a c letter to you dated February 1,1989. His specific questions about the Mark I containment system and evacuation plans for the Quad Cities Nuclear Power Station (QCNPS), and our responses to them, are detailed in the Enclosure. We hope that you will find this information useful in your further dealings with Mr. Shaff.

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V<t:r %:

Victor Stello, Jr.

Executive Director for Operations

Enclosure:

Responses to Questions on Containment Failure DISTRIBUTION EDO 000431F EDO reading TMurley/JSniezek MVirgilio GHolahan SVarga 0GC GPA/CA VStello DMossburg, PMAS (EDO 0004316) w/cy of incoming MKrebs DDudley w/cy of incoming LLuther VStello EJordan DCrutchfield FMiraglia FGillespie SECY Congressional Affairs Docket file

• PREVIOUSLY CONCURRED Office: PM:PDIII-2* LA:PDIII-2* D:PDIII-2* (A)AD:DRSP35* TECH EDITOR

• Surname: TRoss:km LLuther DMuller MVirgilio Date: 3/20/89 3/20/89 3/20/89 3/20/89 3/17 9 Office: (A)D/DRSP= (A)ADP* NRR/DONRR* NRR/DONRR* f EDO Surname: GHolahan SVarga JSniezek TMurley VSt 1 o Date: 3/21/89 3/21/89 3/29/89 3/29/89 $ /89 Office:

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ENCLOSURE Responses to Questions on Containment Failure I. Questions and/or Concerns Related to Mark I Containments Question 1 - What type of studies produced the conclusion of a possible 90%

failure rate? When'were these studies done?

Comments - The U.S. Atonnc Energy Commission sponsored the Reactor Safety Study in the summer of 1972 to estimate public risks that could be involved in potential accidents at commercial nuclear power plants then in use. Three years later, the results of this study were reported in WASH-1400 (NUREG-75/014), "An Assessment of Risks in U.S. Commercial Nuclear Power Plhhts," published in October 1975 by the U.S. Nuciear Regulatory Commission (NRC).

It is from this report that one' can infer (from Table 5-3, "BWR Dominant Accident Sequences," on page 81) for boiling water reactors (BWRs) with Mark I containments, similar to those at QCNPS, that there is approximately a 90 percent c.obability of containment failure during postulated reacto. core melt scenarios. Nuclear power plant containments were not specifically required to be designed to mitigate core melt accidents.

The principal objective of the Reactor Safety Study was to develop meaningful conclusions about the risks of nuclear accidents, particularly as they compared to public risks from other commercial industries. This study intended to produce realistic risk assessments for potentiel severe accidents of extremely low probability. The likelihood and size of radioactive relehses from potential accident pathways were then evaluated, in concert with probable weather and demographic conditions in the vicinity of the reactor, to calculate environmental and public consequences.

The WASH-1400 analyses concluded that the overall risk of BWRs was equivalent to the risk of pressurized water reactors (PWRs) even though the BWR containment was estimated to provide less mitigation of core melt consequences. This conclusion was drawn because the probabilities for core melt accidents in BWRs were estimated to be lower. Furthermore, NRC still holds the view stated in WASH-1400 that commercial nuclear power plants (including Mark I BWRs) represent an acceptably low risk to public health and welfare because of the extremely low probability of severe accident events (e.g., core melt).

Question No. 2 - When was the Mark I first questioned and what action was taken?

Coments - Safety issues related to Mark I containment performance during i

severe accidents of low probability were first expressed by the i

NRC in 1986.

The NRC staff continues to perform studies on the risks associated with potential severe accidents of extremely low probability at light-waterreactors(i.e.,PWRsandBWRs). These studies still indicate that the Mark I type BWRs do not pose an undue level of public risk. However, to further improve the capability of Mark I containments, the NRC has undertaken a program to evaluate the benefits of additional containment modifications that would enhance the ability of Mark I containments to mitigate the consequences of severe accidents if they occurred. This effort is consistent with NRC's policies to ensure that nuclear plants are constructed and operated ever more safely.

In general, ever since the Three Mile Island (THI) accident, a great deal has been done to reduce even further the potential risks associated with operating nuclear plants. Improved operator training, symptom based emergency operating procedures, and certain plant modifications have been adopted (as part of the post TMI action plan) to reduce the likelihood of core melt accidents and to ensure the containment's ability to mitigate the consequences of an accident. Specifically, one of three major risk contributors, anticipated transients without scram (ATWS), to a core melt accident has been substantially reduced by plant modifications mandated by NRC rule 10 CFR 50.62.

Furthermore, recent studies have shown that the BWR suppression pool has a much greater capability to remove fission products from releases than was recognized by WASH-1400. Consequently, if a severe accident threatens to cause uncontrolled failure of the containment, a new strategy calls for venting-the containment from the wetwell so that all radioactive particulate will be scrubbed out by suppression pool water. This is very different from the previous assumption by WASH-1400 that the containment remains sealed until failure. Additional containment modifications and venting procedures are now being developed ar.d implemented at some BWRs.

Question No. 3 - Under what conditions might the Mark I fail? How quickly after an accident might it fail? How soon after failure would residents need to be evacuated?

Comments - The Mark I containment is expected to fail only as a result of accidents in which the core melts and penetrates the bottom of the pressure vessel. Probabilistic risk assessment (PRA) studies for BWRs indicate that the principal accident sequences for BWRs that might result in such containment failure consists

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of long-term loss of decay heat removal (TW),' station blackout 1 (SBO), anticipated transient'without scram (ATWS) and transients l with multiple failures of safety systems.- l The fresults of PRA studies. generally sh'ow 'a' very low calculated frequency of such events.. Nevertheless, the NRC has. taken specific steps to further reduce the likelihood of 'such accidents.

For instance, ATWS mitigation.has been addressed by 10 CFR 50.62 (see Question No. 2 above). SB0 is being. addressed by 10 CFR:

50.63 which mandates all. nuclear utilities to analyze their vulnerability to SB0 and implement corrective modification.

Given a core melt accident, the containment'could possiblyifail from a variety of mechanisms. For instance,' failure duetto a .!

combination of high pressures and temperatures could occur as a l consequence of excess. steam or noncondensible gases. Another~ . q mechanism,.which is currently the subject of HRC- sponsored research, q involves the potential'.for direct contact between hot core. debris "

i and the containment wall. .Less likely scenarios: include inadvertent failure to isolate' containment following the initiation-of an accident and hydrogen explosion.

It is difficult to predict exactly how'soon after a postulated:

severe accident that'a Mark.I containment might fail. WASH-1400 used estimates as short as 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and as long.as 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> for the " time of release" (i.e., containment failure) following a t severe accident event, depending on the type of severe accident.'

Emergency response procedures provide' guidelines for-identifying and declaring the appropriate emergency action level-(EAL)'- be it an unusual event, alert, site eme'rgency, or general emergency.

Precursors to a core melt accident would certainly-lead plant operators into making a general emergency classification so that evacuation procedures would be initiated promptly. The Quad Cities emergency response plan is not contingent on containment-failure to begin general area evacuations. The intent is to begin evacuating all nonessential personnel from the site and surrounding areas'before a major radioactive release occurs.

Question No. 4 - The Des Moines Register article speaks of a $5,000,000 safety upgrade as a possibility for the Mark I. What actions are being taken if any on upgrading the Mark I to make the containment system more dependable? When will these' actions be accomplished?

Comments - Although the risk from the.BWR Mark I plants is still considered to be low, the NRC staff has proposed to further reduce'overall risk by pursuing a program to improve the performance.of Mark I-containments. A number of safety enhancements have been.

identified (in addition to those described under Question No. 2) that appear attractive in terms.of.their potential to reduce risk. These potential Mark I containment and plant improvements fall into the following six areas: (1).hydrogencontrol,(2)

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3 alt'ernate water supply for reactor vessel injection or-renttiment drywell sprays, (3{ enhanced automatic depres-containment p capability surization (i.e.,-venting), (4,(5) core debris. control, and system reliability,.

.(6) emergency response and operating procedures.. The total

-estimated cost for implementing these improvementsLis estimated ~

by the NRC' staff-to be anywhere between $1.6 and $3.1 million.

These recommendations are being consider:d by the Commission.

Improvementsrelatedto'ATWSandSB0(seeQuestionNo.2)are already mandated by Federal regulations',10 CFR 50.62- and 50.63, respectively. If the Commission goes Lforward with the Mark I improvements, implementation schedules would have to be developed by all affected BWR licensees and approved by the NRC. ' This process would certainly take a year or two.at.least.

Question No. 5 --Is inaction by the NRC due in part to.public apathy of nuclear safety?. Would it help if it were shown.that the public in Iowa is concerned? -

Woulo a Governor's Commission. on Nuclear Safety help.in solving the crisis?

Comments - Public interest regarding' nuclear power continues to be.Very high. The NRC is fully aware of and addressirig all the issues associated with reactor containments and does not' require any assistance. in carrying.out its' regulatory responsibilities.

The NRC has devoted considerable effort in defining a course.of .

renedial action for Mark I containments. . Procedural and hardware changes madel to date, since the Reactor . Safety Study, have resulted in. decreases in the severe core damage frequency..  ;

Furthermore, the Mark I improvement program continues to pursue

-a balanced approach in reducing overall risk in'BWR Mark I plants.

II. Questions and/or Concerns related to Evacuation Plans for the Quad Cities Environs.

I (A) Concern 1 ... but an evacuation during the day would be something  !

close to a second disaster. If you know of anyone to talk' to about this, it would be great.  :

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1 Comments - The Federal Emergency Management Agency (FEMA)~ has.the responsibility for reviewing offsite emergency plans and evaluating the performance of State and local governmental agencies during emergency preparedness exercises. .The NRC j provides a similar oversight function for onsite emergency '

preparedness and evaluates the performance of the' licensee. "

During the most recent full-scale exercise, FEMA identified several concerns about offsite preparedness'at Quad Cities.-

These concerns were subsequently resolved and NRC believes that j the state of preparedness is acceptable for the Quad Cities Station. Specific questions with regard to offsite preparedness can be directed to the Regional Director, FEMA Region VII, 911 Walnut Street, Kansas City, Missouri 64106.

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- Furthermore, the " Emergency 'Information" booklet for Quad Cities, distributed to all local residents, provides phone numbers (most of which are' answered 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> a day) and addresses = l for local, county,: and State agencies responsible for implementing'- ..

offsite emergency and disaster services. In the cases of.

.Camanche or Clinton, the 24-hour information number is(319).

242-5712--(Clinton County l Emergency Management Agency). Officials

,at these agencies should be prepared.to discuss--questions regarding evacuation of Clinton County residents.,

Evacuation of residents,l transients, and workers during a-daytime accident has been addressed in- Clinton County Standard Operating Procedures (50P), revised April-1988.. More.specifically, 1 SOP No. 5 and Attachment B provide the-necessary instructions to

cover daytime evacuations. For copies or explanations of the-contents of; SOPS, FEMA or Clinton. County (see preceding paragraph)'

should be contacted. 1 (B) Concern 2. , Figures released by Public Citizen indicate lit would.take i 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to evacuate the Clinton area-which is at least twice.as long-as it sh;ould be.-

Comment - According to the' Quad Cities. Station Emergency Plan Annex, the-estimated time.for simultaneous evacuation of Clinton, and most of the county; would indeed be approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. FEMA has t' reviewed this evacuation time and.found it reasonable. a

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(C) Concern 3 - There is no visible plan.for the evacuation'of. hospitals or nursing homes.

Comment - S0P No. 7 prescribes the specific instructions and guidelines for evacuation of hospitals and nursing homes.

(D) Concern 4 - The plan for evacuating the Camanche school system seems .;

< to be very minimal. Further, the Superintendent of the system is i supposed to get students to Dewitt but Dewitt-is no longer an evacuation ,.

area. The biggest question is where are the buses to come'from if  ;

an evacuation is ordered.

Connent - Evacuation of Camanche school children is prescribed in S0P-No. 5. Allocation of buses and implementation of appropriate contingencies are prescribed in S0P No. 6. Dewitt is not used as an evacuation area for Camanche school children.

(E) Concern 5 - The evacuation plans for an area should be in a form that the average citizen can read and find out exactly what is supposed .

to happen during an evacuation. The booklets 'sent out by the utility are not' complete enough, and the books put together by the officials are so big that few would care to tackle them.

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5 Comment - The " Emergency Information" booklet for QCNPS sent out by Commonwealth Edison Company appears to be appropriately informative and succinct for most people. However, the actual emergency plans are necessarily extensive and detailed because they must meet regulatory requirements and conform to guidance provided by both the NRC and FEMA. If you have any questions concerning either of these documents, contact FEMA or Clinton County for assistance (see Concern 1, above).

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